1. Field of the Invention
The present invention relates to an apparatus and a method for allowing a femto base station to efficiently perform beaconing in a wireless communication system. More particularly, the present invention relates to an apparatus and a method for allowing a terminal that has accessed a Long Term Evolution (LTE) macro base station to efficiently perform a hand-in to an LTE femto base station in a case where the terminal moves to a region of the LTE femto base station while conforming to the LTE standard in a wireless communication system.
2. Description of the Related Art
In a cellular wireless communication system, a phenomenon occurs where a channel state is deteriorated due to a geographical condition inside a cell, a distance between a terminal and a base station, or movement of a terminal, and thus communication between the terminal and the base station may not be performed reliably. For example, a shadow area is formed due to a closed building, such as an office and a house, even inside the coverage area of a base station. If a terminal is located in the shadow area, a base station may not reliably perform communication because a channel state associated with a terminal is poor.
Accordingly, the wireless communication system provides a femto-cell service for providing a high-speed data service while addressing a service problem of a shadow area. The femto cell denotes a small cell area formed by a compact base station that is installed inside an office or a house and that accesses a mobile communication core network via a broadband network. The compact base station is a base station of small power directly installed by a user, and may be called a micro base station, a self configurable base station, an indoor base station, a home base station, a femto base station, and the like. In the following description, the compact base station is referred to as a femto enhanced Node B (eNB).
In a network where a macro eNB and a femto eNB are installed, when a center frequency of the macro eNB and a center frequency of the femto eNB are different from each other, there is a high possibility that a terminal may not recognize a signal of the femto eNB even when the terminal enters the region of the femto eNB. In this case, the terminal is not handed-in to the femto eNB while maintaining connection with the macro eNB.
To address this problem, in a case of a Code Division Multiple Access (CDMA) femto eNB, a method for transmitting a beacon signal for each Frequency Assignment (FA) has been suggested as a beaconing method for allowing a femto eNB to inform a terminal of existence of the femto eNB. That is, a CDMA femto eNB sets a CDMA frequency field cdma_frequency of a CDMA Channel List Message (CCLM) for each FA to an operation frequency and transmits the same. A terminal that receives this is synchronized with the CDMA frequency to perform a hand-in to the CDMA femto eNB.
However, the Long Term Evolution (LTE) and the CDMA are different not only in a transmission method in a physical layer but also in a message format used in an upper layer. Therefore, development of a method suitable for an LTE femto eNB is required.
A terminal may not recognize a signal of the femto eNB even when the terminal enters the coverage area of the femto eNB. Accordingly, a method for changing a System Information Block (SIB) message of a 3rd Generation Partnership Project (3GPP) LTE standard has been suggested. However, a method for changing an SIB message suggested by the LTE femto eNB does not conform to a current 3GPP standard, and thus a compatibility problem with a terminal occurs.
Therefore, a need exists for an apparatus and a method for allowing a terminal that has accessed an LTE macro eNB to efficiently perform a hand-in to an LTE femto eNB in a case where the terminal moves to a region of the LTE femto eNB while conforming to the LTE standard in a wireless communication system.